(This is not one of my areas of expertise so feel free to comment any corrections and such.)
Hot chocolate seems to maximize theobromine content.
"theo" as in theology, for "gods", and bromine comes from broma, for food. So, "food of the gods".
theobromine, chemistry basics of, at erowid,
theobromine, wiki page for,
theobromine poisoning, wiki has a separate entry for,
ancient chocolate alcoholic beverage,
theobromine, best food sources for,
(Top food source is 2,634 milligrams per 100 grams, .. or 2.6%?)
(Elsewhere on the internet it says theobromine is in small amounts in "kola nut (1.0-2.5%), the guarana berry, and the tea plant."
theobromine, drugbank webpage for, (gives "mechanisms of action"),
brain sweat (optional),
theobromine 2011 paper (puzzling), http://www.chem.ucsb.edu/~devries/groupsite/pub/24AP-TB%20alt%20base%20pair.pdf
theobromine 2011 paper, (The de Vries lab photo. I recognize Goleta Beach in the background there. http://www.chem.ucsb.edu/~devries/groupsite/index.htm )